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Copyright N°_ 



CfiKRIGHT DEPOSIT. 




X 



I N 3) B Z 



Experiments on Nebraska Pit-Run Gravels by 
aha Testing Laboratories under direction 
of A. G. Arena, Omaha Oity Engineer Page 1 

Physical Characteristics of Aggregates Page 4 

Compression Strengths at end of 28 days Page 4 

Bulging Effect of Water on Sand & travel—- Page 6 

Releti on of Compressive Strength to fineness 

of Aggregate snd mixture ■ ■ — - Page 7 

Report by Modjeski & - : .ngier on Compressive 
strength — Page 9 

Dept. of Agriculture Screen Analysis and 
compressive strength tests ■ — Page 10 

Compressive strength tests by Clark E. Mick- 
ey on Schuyler and Fremont -Ames Projects Page 12 

r ' iaha City Engineers void and Compressive 

strength tests — — , -- Page 14 

Limestone and Sand-Gravel comparisons by 

Omaha Testing Laboratories Page 15 

Comparative compilations of tests by Lyrnan- 

Richey Sand Co. ■ Page 17 

Discussion of the Concrete Yield for various 
combinations of Nebraska Sands and Gravels, 
by western Laboratories, Inc. and conclusions 
drawn from same Page 19 



©CI.A677156 



JUN-7'22 



EXPERIMENTS ON NEBRASKA PIT -RUN GRAVELS 

INTRODU CTION. 

As is well known to most of us many experiments have "been 
performed "by Prof. R. W. Crura of Iowa, and Prof. Duff Abrams of the 
Lewis Institute of Technology, on proportioning crushed stone, 
screened gravel and pit-run gravel in the designing of a concrete 
mixture. Prof. Crum has come" to the conclusion that any gravel may 
"be used in concrete provided the cement is varied with the sieve an- 
alysis of the gravel on hand. Therefore the engineering department 
of the City of Omaha has deemed it of value to experiment with 
Nebraska gravels in order to determine which sieve should "be used as 
the dividing line "between sand and gravel and then to determine what 
relative amounts of these would produce the "best concrete. The ex- 
periments were conducted by the Omaha Testing Laboratories under the 
direction of Mr. A. C. Arend, City Engineer. 

The experiments were divided into four series. In Series 
No. 1 the No. 10 sieve was used as the dividing line "between the 
fine and coarse particles. Table No. 3 shows in what proportions 
the fine and coarse materials v/ere mixed. The cement used with 
each mixture is also shown on the same table. 

In series No. 2 and 3, the No. 8 and No. 4 sieves were 
used respectively to separate the pit-run gravel into fine and 
coarse. The mixtures are shown in table No. 4. 

Series No. 4 consisted of five pit-run gravels, which were 
used without remixing in any way. In one of these gravels, we used 
more water than necessary and one of them was not as well graded as 
the rest. Table No. 5 gives the mixtures used. 

For the first three series a pit-run gravel was separated 
and recombined in the proportion shov/n. The pit-run gravels used 
in the last series were obtained from local yards and represented 
several pits from which Omaha gets its supply. 

The specific gravity, weight per cubic foot and voids were 
determined by the methods adopted by the American Society of Testing 
Materials. The voids were calculated from the weight per cubic foot 
and the specific gravity. In this connection we wished to check up 
a device which has been used by some laboratories. It consists of 
two cubical boxes arranged one above the other and connected by a 
rubber tube. The water from the upper box rises through the gravel 
in the lower box. When the water appears at the top of the gravel, 
the per cent of voids is read directly on a scale on the upper box. 
We found that for ordinary pit-run gravels the actual voids by this 
device checked very well with the theoretical, but with fine sands 
the results are low. That is due to the fact that the water rises 
so slowly that capillary action interferes with the displacing of 
the air bubbles. In any case this device tends to give low results. 

The test pieces were made in cylindrical molds 4 M x8". 
Enough water was used to produce a mortar which when piled into a 
cone, would flatten slowly. A tapered glass rod was used to rod the 

Page -1- 

) 3 est unnnn [C3 I into I hfuihh mwiczmm/un t*r ■ n i-»- ■ ■ »■».. .-i..-.'.™.. .-■■ — - ~ 



concrete while the molds were filled. The molds were capped with 
glass plates. 

The test pieces were made and stored in a room having a 
temperature of a"bout 70 degrees P. They were removed from the molds 
24 hours after they were made, weighed and immersed in water for 14 
davs, after which they remained in air till broken. The gravel used 
was air dried, the weight of a cubic foot of cement was taken as 94 
pounds. 

Only the 28 day compression test was made. Each value 
given in the tables is the average of three or more tests. 

The Cement used passed all the tests. 

THE RESULTS. 

Table No. 1 shows the physical characteristics of the sand 
and gravel mixtures used. For convenient reference each mixture was 
given a number. Table No. 2 gives the characteristics of sand and 
gravels in general. 

In table Mo. 1 we notice that the weights per cubic foot 
of gravel aggregates are unusually high. The results are accounted 
for by the fact that we used the aggregates in compact form. The 
so called loose volume method would not give uniform results. 

The sieve analysis given in this table show that Nebraska 
pit-run gravels are graded fairly well. The amount passing the No. 
100 sieve is less than 2%, The amount retained on the No. 4 sieve 
is about 35$ of the amount retained on the No. 10 sieve. 

In tables 5, 4 and 5 are tabulated the results of compres- 
sion in pounds per square inch. With but two exceptions all mix- 
tures where one" part of cement to three parts aggregate was used the 
compression strength produced was more than 4000 pounds per square 
inch. As our testing machine did not register above 4167 pounds per 
square inch, all results above this figure are marked "plus". 

The results indicate that the strength increases as the 
coarseness of the aggregate increases, but the increase is not mark- 
ed until we reach a point where more than 50$ of the aggregate is 
retained on the No. 10 screen. Theoretically the mixture in^which 
the sand and gravel are in equal amounts should give the maximum 
strength, because this mixture has least voids but coarser mixtures 
actually do give more strength because they require less water. 

In Table No. 5 we notice that two of the gravels gave 
comparatively low results. In one case, 4-B the gravel is not well 
graded and the other case, 4-D we used water in excess. 

Curve B was constructed from series 1 and 4, table 3 and^ 
5. These curves show quite clearly the relation between the material 
retained on the No. 10 sieve and the resulting compression strength. 
Curve C was constructed from series 2 and 3. It shows the relation 
between material retained on the No. 4 sieve and the resulting com- 
pression strength. 

Page -2- 



The results of these experiments indicate that to get the 
strongest concrete the aggregate should contain 50 to 60$ of mater- 
ial retained on the No. 10 sieve, and that 15 to 25$ of the entire 
aggregate should be retained on the No. 4 sieve. 

In all the mixtures used in these experiments, we noticed 
that the weights per cubic foot of the green concrete were not as 
high as they should "be theoretically. It occurred to us that the 
bulging effect of water on dry sand and gravel might furnish an ex- 
planation. Curve A shows the increase in volume caused by the addi- 
tion of water to the dry aggregate. As was anticipated, a finer 
gravel bulges more than a coarse one with the same amount of water. 
Surface Tension is given as the cause. When enough water is added 
to thoroughly wet and cover the aggregate, the volume shows no in- 
crease. This fact was also anticipated because at this point, Sur- 
face Tension is reduced to a minimum and the particles move freely. 

It is possible to approximate the amount of water in ag- 
gregate by visual inspection. If the particles appear damp the 
percent of water by weight is from 1 to 2} if damp and sticky, 2 
to 5: if the water is visible in globules, 5 to 10; and if the water 
begins to separate, 10. Above 10 percent the water separates easily 
from the aggregate. The gravel as used on the work generally con- 
tains from a trace, to 1% of water. 

From the above results it is easy to explain why the green 
concrete is not denser than is found by experience. If we take any 
pit-run gravel mixture and note the amounts of the various materials 
entering into a cubic foot of the green concrete, we find that the 
increase in volume is governed almost exactly by the bulging effect 
of water on the aggregate used. As an example take mixture A-6, 
from Series No. 1. In making this mixture we used a cubic foot of 
aggregate weighing 116.6 lbs., 14.5 lbs. cement and 13 lbs. of 
water. The total material used was 144 lbs. The volume of green 
concrete was 1.055 cubic foot. The green concrete weighed 136 lbs. 
per cubic foot. Therefore the increase in volume was 5.5$ and since 
the aggregate had a voidage of 28# the decrease in volume should 
have been 11#. Therefore this mixture increased the volume by 16. 5$, 
After allowing 20$ of the water for the cement it leaves us an ag- 
gregate containing 8.7$ water, which, according to the curve has a 
bulge of about 17$. Any other mixture may be figured in the same 
manner. 

This shows to us that although it is desirable to use as 
little water as possible in making concrete, at the same time, we 
are producing a concrete which does not have the maximum weight per 
cubic foot. 

It is also evident from the Curve A that the contractor 
who uses wet gravel by volume in proportioning concrete, is really 
using a richer cement mixture than he intends to. In case of a fine 
pit-run gravel, where the specifications call for 1 to 5 mixture 
the contractor will actually produce about a 1 to 4 mixture if he 
uses wet material. 

Page -3- 



PBLE 
tiO. I. 



Physical Characteristics of aggregates - 



ERIES 



l-fl 



MIXTURE 



SO -2.0 



-a - 10-30 



l-C 



l-D 



l-E 



2-fl 



2-B 



2-C 



6O-4O 



50 -50 



4-0 - 60 



85- 15 



75- -25 



65 -35 



3-* 



90 - IO 



3-e 



20 



3-0 



■4-* 



PLATTE fllfEff 



14-8 



4-C 



4-D 



J4-E 



70 -30 



NUMBER 



I 



2805 



S 



10 



11 



12 



ofoVOWS 



WEIGHT 
PER CO. FT. 



27. 33 



27- IS 



24-. 99 



ZG 19 



26-4-+ 



26. 84 



2.6.50 



24.92 



z+.on 



25.43 



13 



14- 



15 



16 



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3o.o9 



SPECIFIC 

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11665 



11 7. e 1 



MS. 05 



121. SO 



/ 18-63 



119.25 



I 18 61 



I 1 9.00 



12.1.72 



1 23. IO 



1 20- 79 



/ 19. IO 



113.47 



27.84 



26. 45 



,23.57 



J 13.33 



2 60 



260 



2.60 



2. 60 



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ze>o 



2 GO 



zeo 



2 60 



2 60 



p.ioo 



z^a 



2.17 



1.86 



1.55 



i.z+ 



2.34 



2 oe> 



1. 79 



1.95 



174 



2. 60 



2.67 



Z60 



263 



120.6/ 



I 1 7. 26 



263 



261 



i.s;2 



I. 00 



J. 25 



tf.lOO 



97-52 



9 7 83 



9Q. 1 4- 



98 45 



9876 



9766 



97-94- 



98 21 



9805 



98 26 



R.50 



£3 13 



8S28 



8 7 38 



83 ^S 



91.59 



81 13 



83.35 



8S57 



88 57 



8984 



98 4-8 



99 00 



2.00 



3.60 



0.75 



98-75 



98-00 



96 40 



93 ze 



91. I I 



91. JO 



96.35 



8 9. 90 



l&.OO 



9440 



R30 



48-0 



72- o 



76. o 



SO O 



8+0 



qzz 



•J 5 '-47 



76.74 



7966 



8192 



84.18 



RMO 



ZO.O 



30. o 



*o.o 



50.0 



eo.o 



28 & 



37 O 



45 4 



43.3 



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I 5. O 



Z5. O 



35. O 



R. 4- 



G.O6 



9.1 2 



I 2. (6 



J 5. 20 



18 24- 



6 Jo 



1016 



14,2 



IOO 



496 



559 



S3. 20 



9360 



77.65 



61.75 



89. 20 



4flO 



59 3 



355 



26. I 



51.2 



20 O 



30 O 



J3-4- 



14-9 



8.2 



7.9 



15 8 



c£es "ST Con press ion Strengths AtEIino Of 28 D,rys. 



ill IT TFT 



SUBDIVISION 
OF SERIES 



I 



l-fi-3 



l-fl-4 



l-fl-5 



MGGRE6/3TE 



BY WEIGHT 



P IO 



8O 



80 



80 



P8 



P4 



BY WEIGHT 



R.IO 



20 



20 



Zo 



R8 



R.4 



Sr* voi-i/rte 

CErtEMTTO 
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BVVYEIGHT WTPERtt.FT 
•/oWflTERTO OF FINE fl«P 
AGGREGATE C0RR6E flGG. 



I TO 3 



IT04 



TO 5 



9.34- 



II. I I 



10.73 



WT. PER CUFT C ojIPKESS 



CREEN CON- 
CRETE. 



116.65 



I 16-65 



I J&-65 



STRENGTI 

LBS.PEfl.SQ 



140.40 



139.32 



35.08 



4167 



26IO 



2lo5 



I- A-6 



80 



20 



I TO 6 



1 0.24 



I (6.65 



137/6 



G&O 



I- B-3 



70 



30 



J TO 3 



9. IZ 



/ 17 81 



142.56 



4-I67' 



1-8-4 



70 



30 



I TO 



IO.OO 



in 81 



140.40 



2 7 so 



1-9-5 



70 



3o 



I TO 5 



IO.OO 



117 81 



13 3. 24 



220O 



i-8-6 



70 



30 



I TO 6 



I0 35 



117-8/ 



I 3 5.08 



1 700 



C-3 



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40 



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IO.OO 



I 18 05 



14,2 56 



4167 



l-G-4 



SO 



AO 



I TQ4 



3.5Z 



I 16 05 



14148 



2904- 



l-C-S 



60 



4-0 



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9. 5-8 



I 18- 05 



140.40 



2260 



l-C-6 



60 



4-0 



I TO 6 



IO.00 



I IS 05 



I 39-32 



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- D-3 



50 



50 



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9.12 



12 .GO 



/ 46. 88 



4167 



l-D-4 



50 



50 



i T0 4 



9.33 



I 2 I. SO 



145.26 



3070 



I-0-5 



so 



50 



I TO 5 



8.65 



/ 21. 60 



14256 



2426 



I- D-6 



50 



SO 



I TOG 



S.&5 



\Z\ GO 



\A-0 4-0 



I 6 OO 



l-E-3 



40 



I- E-4 



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/ - F. - 5 



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60 



60 



60 



I TO 3 



8.4Z 



I 18.69 



14796 



4-167 



J T04 



3.33 



I IS 69 



I4-5-80 



3805 



I TO 5 



8. 27 



US 6 J 



I ++.12 



29 SO 



l-E-6 



4o 



GO 



Page 



^r 



I TO 6 



8.24 



118 69 



14148 2375 



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MODJESKI & ANGIER 
INSPECTING CIVIL ENGINEERS . 

Chicago, 111. Aug. 19, 1915. 



Gentlemen: 



We are pleased to hand you herewith results of our 
twenty eight day tests on concrete materials for the World Herald 
Building, Omaha, Nebr. , 



Mix 1:2:4 



7 Days 

Per Sq. Inch 

1480 Lbs 

1630 Lbs 

1555 Lds 

Mix 1:4 



7 Days 

Per Sq. Inch 

1940 Lbs 

2050 Lbs 

1995 Lbs 



Dewey Cement, Platte River Sand & Crushed Stone 
Compressive Strength 



28 Days 
Per Sq. Inch 
1790 Lbs 
2090 Lbs 
1940 Lbs 



Average 

Dewey Cement "Sand-Gravel 
Compressive Strength 



Average 



Average 



28 Days 
Per Sq. Inch 
3100 Lbs 
2850 Lbs 
2975 Average 



The figures given above are conclusive evidence that 
your sand-gravel mixture is superior for concrete purposes to 
the Platte River sand with crushed stone mixture; confirming 
our opinion expressed in seven days report. 

Yours very truly, 

MODJESKI & ANGIER 

(Signed) J. J. Reeves, Mgr. 



Page -9- 



UNITED STATES DEPARTMENT OF AGRICULTURE. 
BUREAU OF PUBLIC ROADS. 



Washington, D.C. 



June 23, 1919. 



REPORT ON SAMPLE OF SAND-GRAVEL 



Laboratory No. 14418 

Name of Material, SAND-GRAVEL 

Identification marks, 1930495 & 96 ON BAGS. 

SUBMITTED BY LYMAN-RICHEY SAND CO., FREMONT, NEBR. 

Sampled June 9, 1919 Received June 13th, 1919. 

Sampled from CAR. 

Quantity represented, 360 ACRES, 30 FEET DEEP. 

Source of material, Fremont, Dodge County, Nebraska. 

Location used or to "be used, NEBRASKA FEDERAL AID PROJECT NO. 81. 

Examined for USE IN WEARING COURSE, ONE-COURSE CONCRETE PAVEMENT. 



TEST RESULTS 



SAND 
echanical Analysis) 



GRAVEL 
(Mechanical Analysis) 



•action <f : Fraction € 

tained on 1/4 W screen . . . . 14.7 : Passing 3/4" retained on l/2 tt 2.0 

.ssing 1/4" retained j Passing 1/2" retained on 1/4" 12.7 

i 10 Mesh 44.4 : Passing 1/4" screen 85.3 

.ssing 10 retained on 20 Mesh 27.9 J 



tssing 20 

issing 30 

issing 40 

issing 50 

issing 80 



retained on 30 
retained on 40 
retained on 50 
retained on 80 
retained on 100 



issing 100 retained on 200 



5,5 
3.1 
1.3 
1.9 
0.2 
0.5 



assing 200 Mesh 0.5 



Total 



100.0 



Total 



100. 



Loss "by washing (Silt & Clay) 0.4# 



Character of material: 
Sample consists essentially of 
rounded fragments of granite, 
quartz and quartzite with a large 
amount of sub-angular quartz sand. 

(Signed) 

P. W. J. Milson 

Acting Director. 



Page -10- 



UNITED STATES DEPARTMENT OP AGRICULTURE. 
BUREAU OP PUBLIC ROADS. 
Washington, D.C. 

June 23, 1919. 



Laboratory No. 14418 

Name— SAND-GRAVE L 

Identification marks, ±930495 & 96 ON BAGS. 

SUBMITTED BY LYMAN-RICHEY SAND CO.. FREMONT, NEBR. 

Sampled June 9, 1919 Received June 13th, 1919. 

Sampled from CAR. 

Quantity represented, 360 ACRES, 30 FEET DEEP. 

Source of material, Fremont, Dodge County, Nebraska. 

Location used or to "be used, NEBRASKA FEDERAL AID PROJECT NO. 81. 

Examined for USE IN WEARING COURSE, CEMENT CONCRETE PAVEMENT. 

TEST RESULTS 

Crushing strength, 6 W x 12* cylinders, age 7 days. 

Total Load, Lbs. Unit Load, Lbs. per square inch 

A B 

58350 57780 
6 5940 58180 

62145 57980 Average 



A 


B 


2065 


2040 


2330 


2060 



2198 



2050 



Average 



A- Proportion by volume 



B- Proportions by volume 



(1 part cement 

(3 parts No. 14418 (Sand-gravel) 

(1 part cement ) Accepted 

(1-jt parts Potomac River Sand ) as 

(3 parts Potomac River Gravel) Standard 



(Signed) P. W. J. Milson 

Acting Director. 



Page -11- 



COPY 



STATE of NEBRASKA 

Samuel R. McKelvie, Governor 

LINCOLN 



February 14, 1921 



Lyman-Richey Sand Co., 
Omaha, Nebr. 

Attention: L. C. Curtis. 
Gentlemen: 

In reply to your letter of February 10th. 
asking for the average of the compression tests made 
on the concrete used in the concrete pavement of 
Project 58-A Schuyler-Platte River, you will find here- 
with table stating the average of the 28 day tests for 

the various months. 

1:3 Mix 
Month Average Compressive Strength 



June 
July 

August 



3472 
3115 
3733 



CEM:FP. 



Yours very truly, 

Clark E. Mickey 
Consulting & Testing Engineer, 

Page -12- 



COPY 



STATE of NEBRASKA 
Samuel R. McKelvie, Governor 
LINCOLN 

February 14, 1921. 

Lyman-Richey Sand Co., 
Omaha, Nebr. 

Attention: L. C. Curtis. 
Gentlemen: 

In reply to your letter of February 10th. 
asking for the average of the compression tests made 
on the concrete used in the concrete pavement of 
Project 81, from Fremont to Ames, you will find here- 
with table stating the average of the 28 day tests for 

the various months. 

1:3 Mix 
Month Average Co mpress ive S trength 

May 3464 

June 3589 

July 3644 

September 3130 

Yours very truly, 

Clark B. Mickey 

Consulting & Testing Engineer. 

CEMiFP. 

Page -13- 



OFFICE OF OMAHA CITY ENGINEER 
TESTS BY OMAHA TESTING LABORATORIES AUGUST 1919 



Voids 

Omaha test (3 samples) (28.53) 
Omaha test (3 samples) (25.52) 



Average 26.92, 



Silt Test s. 
From 0.9$ to 2.1B% volume measure. (Allowable, 7$ by volume.) 

Colorimet ric Test. 
Practically clear in each test. Hence free from organic matter. 



Crushing Tests 

8x8x16 Cylinders 

Ends set in Plaster of Paris. 

Cement Sand-Gravel 

1-3 Extra Strong 

l-3-| For Concrete Paving 

1-4 For Heavy Sidewalks Heavy Walls 

1-5 For Heavy Traffic Paving Base 

1-6 For Light Traffic Paving Base 



7da. 
# sq. in. 
5187 


28da. 
# sq..in. 
4260 


105da. 
# sq.in. 
4516 


2300 


3497 


4500 


1866 


2974 


3800 


1048 


2482 


3037 


554 


1347 


2003 



Page -14- 



W. H. Campen, Manager. 

THE OMAHA TESTING LABORATORIES, INC. 

OMAHA, NEBR., Sept. 15th, 1921. 

RELATIVE STRENGTH OP CONCRETE MADE PROM NEBRASKA CRUSHED LIME- 
STONE AND SAND GRAVEL. 

By W. H. Carapen 

These experiments were conducted to study the concrete 
made using limestone in one case and sand-gravel in the other. 
The object in view was to determine the strengths produced "by 
both kinds of concrete, and also to observe the yields. A num- 
ber of Nebraska Civil Engineers engaged in paving work give the 
contractors the option of using one part cement, two and one- 
half parts sand and five parts crushed stone by volume or one 
part cement to five parts sand-gravel by volume. The main part 
of our experiments consisted of determining whether or not the 
mixtures were actually equal in strength. 

We selected two ordinary crushed limestones, one from the 
Louisville quarry and the other from the Weeping Water quarry. 
The sand-gravel used was taken from a pile in Omaha and was be- 
ing used for the construction of concrete base. The sand-gravel 
had been shipped from the Fremont pit. The stone weighed 90 lbs 
per cubic foot and contained 47$ voids. The sand-gravel weighed 
101 lbs. per cubic foot (loose volume) and contained 25$ voids. 
Its screen analysis was as follows: Retained on a #10 screen, 
56$; retained on a #4 screen, 14$; passing a #100 screen, 1$} 
Tested cement was used. 



The actual experiments consisted of making test cylinders 
4" x 8", of 1 to 5, 1 to 5k and 1 to 6, using sand-gravel, and 
of 1 to 2,\ to 5 using the two limestones. Six test pieces were 
made of each mixture and these were broken at the end of 7 and 
28 days. 

As the sand-gravel is often used in a damp condition, test 
pieces were made from material to which water had been added be- 
fore proportioning. 

The results of the experiments are shown in the following 
table: 



Material used: Mixture: Volume yield: Wt. Green 

concrete 



Compression 



Sand gravel 

(dry) 
Sand gravel 

(dry) 
Sand gravel 

(dry) 
Sand gravel 

(wet) 
Sand gravel 

(wet) 



1 cement no change 

5 sand gr 

1 cement no change 

5-J- sand gr 

1 cement no change 

6 sand gr 

1 cement 16$ decrease 
5 sand gr 

1 cement 16$ decrease 
5| sand gr 

Page -15- 



concret 
per cu. 


e 
ft. 


lbs per sq.in. 
7 das. 28 das. 


143 




788 2128 


142 




990 1833 


141 




500 1168 


141 




902 2310 


141 




767 2011 



--2-- 



continued: 



Material used: Mixture: Volume yield 

concrete 



1 cement 16$ decrease 
6 sand gr 

1 cement 10$ increase 
2% sand 
5 stone 
Weeping Water 1 cement 10$ increase 
limestone 2,\ sand 
5 stone 



Sand gravel 

(wet) 
Louisville 

limestone 



Wt .Green 
concrete 
per cu. ft. 

140 

150 

150 



Compression 

Ids per sq.in. 
7 das. 28 das. 



517 
644 

565 



1342 
1416 

1038 



The results as anticipated "by the author show two distinct 
features; viz, damp sand-gravel decreases the concrete yield 
"by 16$ computed on the volume of sand-gravel taken and the 
compression strength is greater than the corresponding mixture 
in which dry gravel was used. The volume shrinkage shows that 
a 1 to 5 mixture using damp gravel gives a concrete containing 
about 24$ cement. 

From the above data it is evident that to obtain a con- 
crete equivalent in strength to a 1, 2j, 5 stone mixture one may 
use a 1 to 5f or even a 1 to 6 gravel mixture. 



Page -16- 



LYMAN-RICHEY SAND CO. 
Omaha, Nebr. 



COMPARISON OF TESTS 
l:2:4--Stone Mix28 days 
Modkeski & Angier, Chicago, 1915 

ll8&i5--Stone Mix 



1940# 



Omaha Testing Laboratories, 1921 



1:4 Sand-gravel 



Mod.jeski & Angier, Chicago, 1915 
Omaha City Engineer 1915-6 
Omaha Testing Laboratories, 1921 

1:5 Sand-gravel 

Omaha City Engineer, 1915 
Omaha Testing Laboratories, 1921 

l:5i Sand-gravel 
Omaha Testing Laboratories, 1921 

1:6 Sand-gravel 
Omaha Testing Laboratories, 1921 



1416 

1038 Average 1227# 



2975# 
2974# 
3070# Average 3006# 



2482# 

2428# Average 2455# 



2011# 



1342# 
1760# 
1800//- 
2375# Average 1804# 



Page -17- 



LYMAN-RICHEY SAND CO. 
Omaha, Net>r. 



1:4 Sand-gravel mix shows over 1000# greater strength than 
1:2:4 Stone mix. 



1:5 Sand-gravel mix shows over 1200# greater strength than 
1:2-^:5 Stone mix and over 500# more than 1:2:4 Stone mix. 

l:5j Sand-gravel shows nearly 800# greater strength than 
1:2^:5 Stone mix and to "be slightly stronger, or equal to 1:2:4 
Stone mix. 



1:6 Sand-gravel shows nearly 600# more strength than l:2|-:5 
Stone mix and within 200# as great strength as 1:2:4 Stone mix. 



Page -18- 



WESTERN LABORATORIES 
Consulting And Testing Engineers 
132 North 12th Street 
LINCOLN, NEBR. 



November 15, 1921. 

Mr. L. C. Curtis, 
General Sales Manager, 
Lyman-Richey Sand Company, 
Omaha, Nebraska. 

Dear Sir:- 

In compliance with your recent request I wish to submit 
the following brief summary of the purposes of the investigations 
of concrete we are now conducting and the information which should 
be obtained from these investigations. 

The purpose of these investigations is to determine the 
physical properties of concrete that is actually being produced for 
concrete pavement foundations by the use of Nebraska gravel contain- 
ing various proportions of material retained on the 10-mesh sieve. 

A large proportion of the determinations will be made up- 
on samples that are prepared under actual working conditions which 
are common to concrete pavement base construction. A part of the 
samples being made under working conditions are being molded on the 
street on paving jobs at the time of construction. When taking 
these samples all the details of construction are left exactly as 
is common for this class of work and the samples are molded after 
the concrete is deposited on the subgrade and graded. These samples 
are molded in such a way that they are truly representative of the 
condition of the concrete in the base, that is the material is not 
tamped in the mold but simply placed within the cylinder and a thin 
strip passed round the inside of the mold to flush the material to 
the surface so that the outside of the sample is no more porous 
than other parts. 

Other samples will be molded to the same consistency in 
the laboratory. The laboratory samples will be tested to deter- 
mine thsir compressive strength, modulus of elasticity, coefficient 
of expansion and expansion due to water absorption. The purpose 
of the last group of tests is to determine the stress produced in 
the base due to changes in temperature and changes in moisture 
content when varying proportions of cement are used in the mixture. 
From the information thus obtained it will be possible to determine 
whether a mixture can be used which will have the proper compressive 
strength to withstand the stress produced by expansion and thus 
eliminate all heaving and crushing of the concrete base from that 
cause. 

Page -19- 



L. C. C. #2. 

It is a fact that the modulus of elasticity of concrete 
varies with the proportions of the mixture, the modulus increasing 
with an increase in the cement content while the coefficient, of 
expansion seems to be oractically the same for all mixtures. This 
being the case it may develop that a better concrete foundation 
for pavements may be produced by reducing the cement content of the 
mixture and thus reducing the modulus of elasticity which will in 
turn reduce the stress produced by changes in temperature. The 
compressive strength will necessarily be reduced but may still be 
great enough to withstand this stress. On the other hand the com- 
pressive strength may also be increased by changing the amount of 
material retained on the 10-mesh sieve to some other proportion 
than is now in common use. 

It is doubtless true that the proportion of aggregate 
retained on the 10-mesh sieve should be varied for the various pro- 
portions of cement in order to produce the best concrete possible 
for that mixture. As an illustration, if the best results may be 
produced in a 1:3 mixture having fifty per cent of the aggregate 
retained on the 10-mesh sieve it is practically a certainty that 
such a proportion of aggregate retained on a 10-mesh sieve will 
not give the greatest strength in a 1:6 mixture. When these in- 
vestigations are completed it should be possible to state what the 
proportion of aggregate retained on the lu-mesh sieve should be 
to produce maximum strength for the various proportions of cement 
and aggregate under actual concrete foundation construction con- 
ditions. 

Information on the 28-day strength tests on a 1:5 mixture 
laid for a pavement foundation should be complete by January 1, 1922 
while the laboratory investigations on various mixtures, prepared as 
outlined above, should be completed by April 1, 1922, including 28- 
day strength tests, determinations of modulus of elasticity and de- 
terminations of coefficient of expansion. 

Other information incidental to these investigations will 
be obtained as progress is being made and will also be forwarded to 
you. 

Yours truly, 

WESTERN LABORATORIES, 

By Roy M. Green, Mgr. 



Page -20- 



A DI SCUS SION OF THE CONCRETE YIELD FOR VARIOUS COMBINATIONS OF 

NEBRASKA SANDS A ND GRA VELS. 

By 
Roy M. Green, 
Manager, Western Laboratories, 
132 North- 12th St., 
Lincoln, Nebraska. 



PURPOSE OF DISCUSSION. The purpose of this discussion 
is to show the effect of different amounts of moisture upon the 
volume of combinations of Nebraska sands and gravels and to show 
the concrete yields for these materials when measured by differ- 
ent methods and while containing various percentages of moisture. 
The weight of the aggregate necessary to produce one cubic foot 
of concrete from these materials will also be shown as well as 
the quantity used in making concrete of one inch Nebraska lime- 
stone and pit -run sand. 

METHOD OF MAKING DETERMINATIONS OF WEIGHT PER CUBIC 
FOOT OF AGGREGATE. The method of making determinations of the 
unit weight of aggregate was the standard of the American Society 
for Testing Materials, C-20-21. 

The equipment for this determination consists of a bal- 
ance, cylindrical container 10-inches in diameter by 11-inches 
high, and a metal* rod 3/4-inch in diameter and 18-inches long, 
tapered to a blunt point. 

The cylinder is first calibrated by weighing it empty, 
then repeating the weight with the container filled with water. 
The test is made by introducing enough aggregate into the cylin- 
der to fill it one-third full. The material is then tamped with 
the rod twenty-five times and more material added until the con- 
tainer is two-thirds full. The tamping is then repeated, allow- 
ing the tamper to go only as far into the material as the depth 
of the second layer. The cylinder is then heaped full and the 
tamping process repeated. The excess material is then struck off 
the top of the cylinder with the rod and the whole is weighed. 
From this data the weight per cubic foot of the material is de- 
termined. 

In making the tests herein described the foregoing pro- 
cess was used and in addition determinations were made on the 
material when in a loose condition, the container being filled 
without any compaction whatever. 

RESULTS OF DETERMINATIONS OF UNIT WEIGHT OF AGGREGATE. 

The following curves show the weight per cubic foot of 
different combinations of sand and gravel from the Platte and 
Loup Valleys (Columbus) when the percentage of moisture was vari- 
ed through a wide' range. The following proportions of sand and 
gravel were used in making these tests. 

Page -21- 



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130 



Weight ref? Cubic /^oor o/=" 
Featte Riser Sand and Gravel 
with D/rrERErrr Rercemt- 
AGEs or Moisture. 

~ LOOSE. MEASURE. 

/o% on */o r 9o% RASstr/G */o. 

' ZO% ■< •■ , 80% 

30% " •• , 70% 

Ao% " - , 60% 

Tests Made eor. 

LYMAN- R/Cr/TY 3AM D CO. 

OMAHA, rfEBR. 
BY 

WESTER ti LABORATORIES. 

L./MCOL.n,flE(3R. Hov.Z8/zi. 




-zo 



Rerce/iT or Moisture, by Weight 

Page -22- 




RElRCErtT Or Mo/STU^E, 3Y WEIGHT. 



zo 



Page -23- 



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Weight f>£& Cc/eic rooT or 
^l-atte: Fiver 3am d amd <S/?av 

e1l. with dlftelreht rb.r- 
CFfiTAG£s or Moisture:. 

LOOSE. MEASURE 

50% orr */o, &0% rASSifiG */o. 

00% •• » y IOO% " 

L-YMAfl- PICHEY SAriDC(\ 

Omaha, /Vjebr. 

WESTEFrt LABORATORIES. 

/lev. Z8, 'zi. 




Z A 6 8 JO *Z lA /6 

Perceut or Afo/jTUFE, 3Y Weight. 



Page -24- 



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Page -25- 



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Page -26- 



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Tests Made eor 

LYMAM-RICHEY SAMP CO. 

Omaha, Nebk 
by 

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PEC 13/Zl 



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Page -32- 



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Page -33- 



Sand, Passing Gravel, Retained 
10-mesh Sieve, on 10-mesh Sieve 
Percentage. Percentage. 



90$ 


ioi 


80$ 


20$ 


70$ 


30$ * 


eo$ 


40$ 


50# 


50$ 


40$ 


eo$ 



As an illustration of the results obtained "by these de- 
terminations it was found that for a material having 80$ passing 
and 20$ retained on the 10-mesh sieve (approximately pit-run) the 
weight per cubic foot loose and dry was found to be 109# for Platte 
Valley material and 112# for Columbus material. The weights per 
cubic foot for the same materials dry and compacted, as described 
above, were 115# and 119# respectively. The weights per cubic foot, 
loose measure, for the same materials when swelled to their great- 
est volume by the addition of approximately 3$, by weight, of mois- 
ture were 89# and 90,^ respectively. In other words, in the case of 
the Platte Valley material there were 115# of gravel to the cubic 
foot, compacted, as compared with 86# of sand and gravel per cubic 
foot when loose and containing 3$, by weight, of moisture. In the 
case of the Columbus material there were 119# of material per cubic 
foot of dry and compacted aggregate as compared with only 87# of 
moist material. In other words, there was actually 33.7$ more Platte 
Valley material in the dry compacted measure than when loose and 
moist. In the case of the Columbus material there was 36.8$ more 
material. 

Comparing sand-gravel, that is material having 50$ pass- 
ing and 50$ retained on the 10-rnesh sieve, it was found that the 
dry and compacted material weighed 121# per cubic foot in the case 
of the Platte Valley material and 126# in the case of the Columbus 
material. When moistened with approximately 3$ of water, by weight, 
the same materials weighed 96# and 10S# per cubic foot respectively* 
In other words, with the Platte Valley material there were 121# of 
aggregate, compacted, as compared with 93# per cubic foot when loose 
and containing 3$, by weight, of moisture. In the case of the Col- 
umbus material there were 126# of material per cubic foot of dry 
and compacted aggregate as compared with 99# of sand and gravel per 
cubic foot when loose and containing 3$ s by weight, of moisture. In 
other words, there was actually 30.1$ more Platte Valley material in 
the dry compacted measure than the loose moist material. In the 
case of the Columbus material there was 27.4$ more material. 

SPECIFYING PROPORTIONS BY VOLUME. In view of the fact that 
there is as much as 36.8$ difference in the actual amount of sand 
and gravel in a unit volume, for certain commercial combinations, de- 
pendent upon the method of measurement which is used, and since there 
is practically always at least 25$ difference for any commercial 
Nebraska sand and gravel it should be apparent that it is impractical 
to specif y the proportions of the concrete mixture by volume only, 
without further explanation including a statement of the rninimun 
amount of cement allowable per unit volume of concrete, IN PLACE, 
and expect these specifications to be complied with in the field 

p age -34- 



without working an injustice on one party to the contract. In order 
to "be sure that the correct amount of cement is "being used it is 
absolutely necessary to make the measurement in place "because the 
volume of the aggregate changes so rapidly with changes in moisture 
content, as can be seen "by an inspection of the curves for "Weight 
per Cubic Foot". Since a small change in moisture content produces 
a great change in volume and since the amount of moisture in the 
aggregate is never known at the time the measurements are made on 
the work it is absolutely impossible to be sure of obtaining the 
correct volumes by measurement. The volume should be approximated at 
the beginning of each piece of work, and afterwards checked in place , 
and future quantities of materials based upon such measurements. 

The advantages to this method are that it makes it possible 
for all contractors to bid on work with the definite knowledge of 
exactly how much cement is expected. It also makes it possible to 
obtain the desired amount of cement in the work without causing fric- 
tion between the inspector and the contractor's foreman relative to 
the proper method of determining the amount of aggregate that should 
be used.# 

CONCRETE YIELD. Since there is such a great difference in 
the amount of aggregate contained in a unit volume of material as the 
result of a change in moisture content the resulting yield of con- 
crete is greatly influenced by the condition of the aggregate at the 
time it enters the mixture. When the concrete is mixed to a given 
consistency, however, there is a certain weight of aggregate per uni - 
volume of concrete regardless of the moisture contained in the ag- 
gregate at the beginning. Tests for yield were made upon concrete 
mixed to consistencies such that the fresh mixture showed a slump 
of from 1/2" to 1-1/2 M and from 5" to 7 W . The following table shows 
the yield of concrete per unit volume of aggregate. 



#To the writers knowledge, this method of specification 
was first used in Nebraska on pavement work by Mr. H. H. Tracy, City 
Engineer, Norfolk, Nebraska. 



Page -35- 



con: 


3RETE 


YIELD FOR NEBRASKA SAND 


AND CRAVED COMBINATIONS 


• 


Aggre- 


Mis, 


Approx- 


Cubic 


Feet of 


Concrete 


from One 


Cubic 


Foot of 


gate Re- 


Part 


3 imate 






Aggrega 


te. 






tained 


by 


Slump, 


Dry Compacted. 


Dry L 


Dose. 


Wet I 


joose. 


on 10- 


Vol- 


Inches. 


Colum- 


- Platte 


Colum- 


Piatt 


Colum- 


• Platte 


mesh 


ume . 




bus. 


Valley. 


bus. 


Valley. 


bus . 


Valley. 


Sieve. 


















log 


1:3 


1 


1:22 


1.10 


1.15 


1.05 


.91 


.80 


IQg 


1:3 


6 


1.23 


1.14 


1.16 


1.09 


.92 


.84 


10g 


1:4 


1 


1.16 


1.07 


1.09 


1.01 


.86 


.78 


log 


1:4 


6 


1.18 


1.10 


1.11 


1.05 


.88 


.80 


log 


1:5 


1 


1.13 


1.05 


1.07 


1.01 


.85 


.79 


log 


1:5 


6 


1:16 


1.10 


1.09 


1.05 


.86 


.78 


log 


1:6 


1 


1.13 


1.07 


1.07 


1 op 


.85 


.77 


log 


1:6 


6 


1.13 


1.09 


1.07 


1.04 


.85 


.78 


log 


1:7 


1 


1.15 


1.07 


1.07 


1.02 


.85 


.79 


lGg 


1:7 


6 


1.15 


1.08 


1.07 


1.03 


.85 


.80 


20# 


1:3 


1 




1.15 




1.09 




.85 


zoi 


1: 


3 


6 




1.17 




1.11 




.87 


20f 


1 


4 


1 




1.12 




1.06 




.83 


20f 


1 


4 


6 




1.14 




1.08 




.84 


20f 


1 


'5 


1 




1.08 




1.03 




.80 


20% 


1 


:5 


6 




1.10 




1.05 




.82 


20f o 


1 


:6 


1 




1.07 




1.02 




.79 


20f o 


1 


:6 


6 




1.08 




1.03 




.80 


20$ 


1 


:7 


1 




1.06 




1.01 




.79 


20f 


1 


:7 


6 




1.08 




1.03 




.81 


30# 


1:3 


1 


1.18 


1.15 


1.15 


1.09 


.85 


.87 


30# 


1:3 


6 


1.21 


1.19 


1.17 


1.12 


.87 


.90 


30^ 


1 :4 


1 


1.14 


1.12 


1.10 


1.06 


.82 


.85 


30^ 


1:4 


6 


1.16 


1.14 


1.12 


1.08 


.84 


.87 


30g 


1:5 


1 


1.11 


1.10 


1.07 


1 . 04 


.80 


.84 


30^ 


1:5 


6 


1.15 


1.12 


1.09 


1.06 


.82 


.85 


30£ 


1:6 


1 


1.10 


1.09 


1.06 


1.03 


.79 


.83 


30^ 


1:6 


6 


1.10 


1.10 


1.06 


1.04 


.80 


.83 


30^ 


1:7 


1 


1.09 


1.09 


1.05 


1.03 


.79 


.83 


30^ 


1:7 


6 


1.10 


1.10 


1.06 


1 . 04 


.79 


.83 


40# 


1:3 


1 


1.18 


1.14 


1.12 


1.09 


.91 


.88 


40# 


1:3 


6 


1.21 


1.15 


1.16 


1.11 


.93 


.89 


40^ 


1:4 


1 


1.14 


1.11 


1.08 


1.05 


.87 


.85 


40<£ 


1:4 


6 


1.15 


1.12 


1.09 


1.07 


.88 


.86 


40# 


1:5 


1 


1.10 


1.07 


1.04 


1.02 


84 


.83 


40^ 


1:5 


6 


1.13 


1.08 


1.07 


1.03 


.86 


.83 


4Qg 


1:6 


1 


1.10 


1.04 


1.04 


.99 


.84 


.80 


40^ 


1:6 


6 


1.12 


1.07 


1.06 


1.02 


.86 


.82 


40^ 


1:7 




1.08 


1.04 


1.03 


.99 


.83 


.80 


40^ 


1 


;7 


6 


1.10 


1.05 


1.04 


1.00 


.84 


.81 



Page -36- 



CONCRETE YIELD FOR NEBRASKA SAND AND GRAVEL COMBINATIONS. 




Approx- Cubic Feet of 
imate 

Slump, Dry Compacted. 
Inches. Colum- Platte 
bus. Valley. 



loncrete from One Cubic Foot of 
Aggregate. 

Dry Loose. Wet Loose. 
Colum- Piatt Colum- Platte 

bus. Valley. bus. Valley. 



Sieve. 



50# 
50£ 
50# 
50£ 
50$ 
50£ 

50$ 
50$ 
50^ 
50£ 

60$ 

eoi 

60$ 

eo$ 

60$ 
60$ 
60^ 
60# 
60# 



1:3 
1:3 
1:4 
1:4 
1:5 
1:5 
1:6 
1:6 
1:7 
1:7 



1 
6 
1 
6 
1 
6 
1 
6 
1 
6 

1 
6 
1 
6 
1 
6 
1 
6 
1 
6 



1:13 
1.19 
1.15 
1.15 
1.09 
1:10 
1.06 
1.09 
1.05 
1.08 

1.14 
1.17 

1.08 
1.09 
1 . 04 
1.07 
1.02 
1.05 
.99 
1.01 



1.11 
1.15 
1.07 
1.10 
1.04 
1.06 
1.05 
1.07 
1.06 
1.05 

1.10 

1 » i.v 

1.04 
1.03 
1.02 
1.04 
1.01 
1.03 
1.03 
1.03 



1.11 
1.12 
1.07 
1.03 
1.03 
1.04 
1.00 
1.03 
.99 
1.02 

1.09 

1.12 

1.03 

1 . 04 

1.00 

1.05 

.98 

1.01 

.94 

.96 



1.06 

1.10 
1.03 
1.05 
1.00 
1.02 
1.00 
1.02 
1.01 
1.01 

1.03 
1.05 
.97 
1.01 
.95 
.97 
.94 
.97 
.96 
.96 



,94 
90 
91 
,86 
88 
84 
86 
83 
85 

91 
93 
86 
87 
83 
85 
82 
84 
79 
80 



.85 
.89 
.83 
.85 
.80 
.82 
.81 
.82 
.81 
.81 

.85 
.87 
.81 
.83 
.79 
.81 
.78 
.80 
.80 
.80 



CO NCRETE YIELD FOR COMBINATIONS OF ONE INCH BROKEN ST ONE AffD PITrRUN 

SAND AGGREGATE. 



Mix, Parts 
"by Volume. 



Approximate 

Slump, Inches. 



1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 



2; 3 

2*3 

2:3-1/2 

2:3-1/2 

2:4 

2:4 

2-1/2:4 

2-1/2:4 

2-1/2:5 

2-1/2:5 

3:5 

3:5 

3:6 

3:6 

4:5-1/2 

4:5-1/2 



1 

6 

1 

6 

1 

6 

1 

6 

1 

6 

1 

6 

1 

6 

1 

6 



Cubic Feet of Concrete from One Cubic Foot 
of Combined Sand and Stone Aggregate'. 
Dry Compacted. Dry Loose 



1.05 

1.08 

1.00 

1.03 

.98 

.99 

.97 

.99 

.97 

.97 

.99 

1.00 

.95 

.96 

1.00 

1.00 



1. 


05 


1. 


08 


1 


02 


1, 


.05 


4 


99 


1 


.01 




.98 


1 


.00 




.98 




.98 


1 


.01 


1 


.02 




.96 




.98 


1 


.02 


1 


.02 


Page -37 



It will "be noticed that the concrete yield for the finer 
aggregates is greater than for the coarser materials. The yield 
is also greater for the richer mixtures. This is the natural result 
of the fact that the moisture swells the finer aggregate to a great- 
er extent than the coarser materials and the greater amount of ce- 
ment will, of course, increase the "bulk of concrete if there is more 
than enough to fill the voids in the aggregate. 

For most grades of material and proportions of cement and 
aggregate the yield of concrete is about the same as the volume of 
aggregate used, when measured dry and loose. In other words, if the 
mixture is to "be made on a volume basis it should "be based upon the 
dry loose volume of aggregate. 

It is also interesting to notice that if the mixture is 
made on a basis of wet loose material that the shrinkage may be as 
great as 20f . This emphasizes what has already "been "brought out, 
namely, that specifications should not "be drawn so as to simply call 
for a certain volume of cement to aggregate, "but should also stipu- 
late the actual amount of cement to "be used in each unit volume of 
concrete in place. 

According to the standard definition, "concrete yield" is 
the volume of concrete produced "by one volume of aggregate MIXED AS 
USED. An inspection of the foregoing tabulation shows that the con- 
crete yield of sand-gravel is greater, for many mixtures and just as 
great for all mixtures as the yield of an aggregate made up of one- 
inch stone and pit -run sand. 

There has "been a general impression among many contractors 
that the concrete yield produced "by an aggregate of "broken stone and 
sand is much greater than for sand-gravel materials, for two reasons. 
First, the volume of the sand-gravel used has "been measured in a 
moist and loose condition, when the bulk is the greatest, The mater- 
ial will naturally show a shrinkage from that condition when after- 
wards measured, in place, in concrete. Second, the volume of the 
stone aggregate is taken as the original volume of material, rather 
than the volume of the mixed stone and sand, which should be used 
for comparison. The foregoing table shows the correct yield of a 
broken-stone (1" stone) and sand aggregate. The following table 
shows the erroneous conclusions that may be drawn in this connection, 
if the volume of the stone is taken as the original volume of the 
aggregate entering into a broken-stone-sand aggregate. 



Page -38- 



CUBIC FEET CP CONCRETE PRODUCED FROM ONE CUBIC FOOT OF ONE INCH 







BROKEN 


STONE WITH PIT-RUN 


SAND. 




Mix, Parts 


Approximate 


Concrete Pro- 


Cubic 


i Feet of 


by Volume. 


Slump, Inch 


es. duced from 


Sand 


Used with 






One Cubic Foot 
of Stone, Cubic 


Each 


Cubic Foot 
of Stone. 




1 


Feet. 






1 


:2:3 


1.33 


.66 


1 


:2:3 


6 


1.37 




.66 


1 


:2:3-l/2 


1 


1.22 




.57 


1 


:2:3-l/2 


6 


1.26 




.57 


1 


:2:4 


1 


1.16 




.50 


1 


:2:4 


6 


1.17 




.50 


1 


2-1/2:4 


1 


1.18 




.63 


1. 


2-1/2:4 


6 


1.19 




.63 


is 


2-1/2:5 


1 


1 16 




.50 


1: 


2-1/2:5 


6 


1.15 




.50 


1; 


3:5 


1 


1.25 




.60 


1: 


3:5 


6 


1.26 




.60 


11 


3:6 


1 


1.13 




.50 


1: 


3:6 


6 


1.13 




.50 


l: 


4:5-1/2 


1 


1.38 




.73 


1: 


4:5-1/2 


6 


1.37 




.73 



ECONOMY OF SAND GRAVEL AGGREGATE. If the foregoing method 
of comparison is used it is apparent how erroneous conclusions may 
be arrived at. However, since concrete aggregates are purchased on 
a tonnage basis a real comparison of their cost should therefore be 
based upon the actual weight of material that is necessary for one 
cubic unit of concrete, in place. The following table shows the ac- 
tual amount of aggregate per cubic foot of concrete for various mix- 
tures of cement and aggregate and for different grades of material. 

POUNDS OF AGGREGATE IN ONE CUBIC FOOT OF SAND AND GRAVEL CONCRETE. 



Aggregate Mix, Parts Approximate Pounds of Aggregate per Cubic 

Retained _by Volume^ Slump, Inches. Foot of Concrete, 

on 10-mesh~ ~ ; " Columbus. Platte Valley. 

Sieve. _ *~ 

1 
6 
1 
6 
1 
6 
1 
6 
1 
6 



Page -39- 



10g 


1:3 


10* 


1:3 


10g 


1:4 


log 


1:4 


log 


1:5 


XQg 


1:5 


log 


1:6 


log 


1:6 


lt)g 


l;7 


log 


1:7 



97 


101 


96 


97 


102 


105 


100 


102 


104 


106 


102 


101 


104 


104 


104 


102 


104 


104 


104 


103 



POUNDS OF AGGREGATE IN ONE CUBIC FOOT OF SAND AND GRAVEL CONCRETE. 



Pounds of Aggregate per Cubic 
Foot of Concrete. 
Columbus. Platte Valley. 



Aggregate 


Mix, Parts 


Approximate \ 


Retained 


"by Volume. 


Slump, Inches. 


on lO-mesh 






Sieve. 






20f 


1:3 


1 


20% 


1:3 


6 


zoi 


1:4 


1 


20% 


1:4 


6 


20% 


1:5 


1 


20% 


1:5 


6 


20^ 


1:6 


1 


20# 


1:6 


6 


20# 


1:7 


1 


2Of 


1:7 


6 


zo% 


1:3 


1 


50% 


1:3 


6 


50% 


1:4 


1 


50% 


1:4 


6 


50% 


1:5 


1 


30^ 


1:5 


6 


30# 


1:6 


1 


30£ 


1:6 


6 


30# 


1:7 


1 


50% 


1:7 


6 


Wo 


1:3 


1 


W 


1:3 


6 


Wo 


1:4 


1 


Wo 


1:4 


6 


40^ 


1:5 


1 


Wo 


1:5 


6 


W 


1:6 


1 


40£ 


1:6 


6 


40# 


1:7 


1 


40# 


1:7 


6 


Wo 


1:3 


1 


Wo 


1:3 


6 


Wo 


1:4 


1 


50^ 


1:4 


6 


Wo 


1:5 


1 


Wo 


1:5 


6 


W 


1:6 


1 


Wo 


1:6 


6 


50% 


U7 


1 


Wo 


1:7 


6 





101 




98 




103 




102 




106 




104 




108 




106 




108 




106 


103 


103 


101 


101 


107 


106 


105 


105 


110 


• 108 


108 


106 


111 


109 


111 


108 


US 


109 


111 


108 


106 


105 


103 


104 


110 


109 


109 


107 


114 


112 


111 


111 


114 


115 


112 


112 


116 


116 


114 


114 


107 


110 


106 


106 


111 


114 


110 


110 


116 


116 


114 


114 


119 


115 


117 


114 


120 


115 


118 


114 



Page -40- 



POUNDS OF AGGREGATE IN ONE CUBIC FOOT OF SAND AND GRAVEL CONCRETE. 



60# 


1:3 


60<£ 


1:3 


60# 


1:4 


60# 


1:4 


60# 


1:5 


60# 


1:5 


60# 


1:6 


60£ 


1:6 


60# 


1:7 


60# 


1:7 



Platte Valley, 



Aggregate Mix, Parts Approximate Pounds of Aggregate per Cubic 

Retained by Volume. Slump^ Inches. Foot of Concrete, 
on 10-mesh ~ Columbus. 

Sieve. _ 

1 
6 
1 
6 
1 
6 
1 
6 
1 
6 



109 


110 


106 


108 


115 


116 


114 


112 


119 


119 


116 


115 


121 


120 


118 


116 


126 


118 


124 


116 



POUNDS OF AGGREGATE IN ONE CUBIC FOOT OF BROKEN- STONE- SAND CONCRETE. 



Mix, Parts 
by Volume. 



Approximate 
Slump, Inch* 



Pounds of Aggregate per Cubic Foot of Con- 
crete. 



One In 
Stone. 



12 


2:3 


1 


12 


2:3 


6 


1 


'2:3-1/2 


1 


1' 


2:3-1/2 


6 


1 


:2:4 


1 


1 


;2:4 


6 


1 


{2-1/2:4 


1 


1 


: 2-l/2;4 


6 


1 


: 2-1/2 : 5 


1 


1 


: 2-1/2: 5 


6 


1 


23:5 


1 


1 


:3:5 


6 


1 


:3:6 


1 


1 


:3:6 


6 


1 


:4: 5-1/2 


1 


1 


:4:5-l/2 


6 



ch Broken 


Sand. 


Total Weight of 






Aggregate t 


68 


52 


120 


66 


51 


117 


74 


49 . 


123 


72 


47 


119 


79 


45 


124 


77 


45 


122 


77 


48 


125 


76 


47 


123 


79 


46 


125 


79 


46 


125 


73 


54 


127 


72 


53 


125 


81 


47 


128 


80 


46 


126 


65 


60 


125 


66 


59 


125 



From an inspection of the foregoing tables it is seen that 
a 1:4 or a 1:5 sand-gravel concrete contains less aggregate than a 
1:2:4 broken-stone-sani concrete, and a 1:5 or a 1:6 sand-gravel con- 
crete contains less aggregate than a 1:3:5 or 1:3:6 broken-stone-sand 
concrete, by weight. In other words, for concretes of equal strength 
there is actually less aggregate used when sand-gravel is used than 
when a combination of broken stone and sand is used. 



QUANTITIES TO BE USED IN ESTIMATING. In estimating the 
amount of material which is necessary for aggregate the following 
blue prints were prepared. The quantities given are such that they 
include the amount of material, by weight, necessary for any mixture, 
due allowance being made for all losses which will normally occur. 

Page -41- 



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Page -42- 



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Page -43- 



Conclusions Drawn from a Consideration of the Concrete 
Yield of Sand-Gravel Combinations. 



1. A small percentage, of moisture may change the volume 
of sand-gravel to such an extent that it is increased as much as 
30$ when measured wet and loose as compared with the same material 
measured dry and compacted. 

2. Specifications should always "be so drawn as to stipu- 
late exactly how much cement is required per unit volume of concrete, 
in place. This is absolutely necessary in order to be fair to both 
contracting parties, on contract work, and in order to have a def- 
inite and fair basis for checking the work. 

3. The concrete yield is greater for sand-gravel than for 
an aggregate made up of one inch stone and sand. 

4. The actual weight, of aggregate in sand-gravel concrete 
is less than for concrete made from broken stone and sand, with 
corresponding strength. 



Page -44- 




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